Optical non-linearities due to charge transfer in type II heterostructures

We present experimental studies of photocreated carrier population in type II heterostructures. The main effects are related to charge separation and band filling : Blue shift and broadening of the luminescence line, transition from indirect recombination to pseudo-direct, and then to direct-type I recombination. They may lead to more complex non-linear effects such as bistability. These effects can be accounted for by theory in the framework of the Envelope-Function Approximation, by self consistent treatment of the Poisson and Schroedinger equations.